(1) Field of the Invention
The present invention relates to synthetic lamellar magnesium phyllosilicate and a process for the preparation thereof. More particularly, the present invention relates to a process for preparing synthetic lamellar magnesium phyllosilicate having a good emulsifying property and a large specific surface area and being excellent in the adsorbing property from active silicic acid or active aluminosilicic acid obtained by an acid treatment of a clay mineral.
(2) Description of the Prior Art
It is known that various magnesium silicate minerals may be synthesized by hydrothermal reaction of starting materials of the MgO-SiO.sub.2 -H.sub.2 O system. For example, it is reported in Journal of the American Ceramic Society, 43, No. 10, pages 542-549 (1960) that when a starting material such as a coprecipitate having a composition of 3MgO-4SiO.sub.2 is subjected to a hydrothermal treatment at 282.degree. C. under a pressure of 950 psi for 168 hours, magnesium silicate having a talc type crystal structure is formed, and that if a starting material having a composition of 3MgO-2SiO.sub.2 is subjected to a hydrothermal treatment at 155.degree. C. under a pressure of 65 psi for 432 hours, a scaly serpentine type crystal is formed and if the same starting material is subjected to a hydrothermal treatment at 282.degree. C. under a pressure of 950 psi for 168 hours, a crysotile type crystal is formed. This research is important in that synthesis of magnesium silicate minerals has become possible. PG,3 However, the minerals prepared according to this proposal have a small specific surface area and a low adsorbing property and are still insufficient in the utility.
Recently, Japanese Patent Application Laid-Open Specification No. 9812/83 proposes a process in which lowly crystalline magnesium silicate hydrate is prepared by subjecting an amorphous silicic acid starting material such as ferrosilicon dust, a magnesium oxide starting material and an aqueous slurry starting material to a hydrothermal treatment under a pressure lower than 9 kg/cm.sup.2, and it is taught that if amorphous silica such as white carbon is used as the starting material, the water repellency of the obtained magnesium silicate is low.